Use Trigger Zone instead of warps.

Put trigger zones around every coin you need to collect, every trigger zone opens one block.

Once you have all 5 coins, all the trigger blocks have dissapeared and you can get through.

If you want you can also put a revert morph and a warp behind.

About the thing with the bottom line of the level, if you don't want to be able to escape easily by flying throught the bottom line simply put some floor there. :P

EDIT:

I know you can't free the bird with TNT, that is why you needed the electro blaster projectile in the crate.